Non-geostationary orbit (NGSO) systems employ constellations of satellites in low earth orbit (LEO) or medium earth orbit (MEO) that sweep across the earth at high rates of speed relative to geostationary earth orbit (GEO) satellites. As such, NGSO systems require a much larger number of terminal (e.g., ground antenna) handovers to be supported than GEO systems. In addition, unlike GEO systems, where terminal handovers are caused solely by terminal mobility (e.g., beam handover), NGSO systems necessarily must support multiple types of handovers including, but not limited to, inter-satellite handovers (due to satellite motion, rotation of the earth, and/or path optimization), inter-gateway handovers (due to rotation of the earth, user terminal mobility, and/or path optimization), link handovers (due to link outages, which may be due to node and/or link failures), and beam handovers (due to satellite motion, rotation of the earth, beam squint, and/or user terminal mobility).
Current solutions for routing NGSO systems employ link-state routing using on-board narrowband internet protocol (IP) routers (i.e. routers on-board the satellites). This approach implies that on-board routers establish and maintain links with their neighboring routers, establish and maintain synchronization of a link-state database at run time, and modulate/demodulate and inspect data packets at run-time in order to make real-time routing and forwarding decisions. As such, the routing for the entire satellite network needs to be updated in real-time each time there is a handover event. Because the entire network has to be updated for each handover event and because the NGSO system connectivity is constantly changing, the network management system must perform a large number of calculations for each update of the routing. Due to scalability issues with link-state routing, this approach does not scale beyond a few hundred satellites and associated links. Further, this approach does not provide a performant or scalable solution for addressing user terminal handover requirements.
There is therefore a need for an improved routing technique that allows for scalability for large NGSO satellite constellations as well as compliance with user terminal handover requirements.